The present invention relates to a method of control, and more particularly, to a method of real-time control of a plurality of power output apparatus for providing a predetermined power output at an optimal efficiency of the combined plurality of the power output apparatus.
In systems which have a plurality of apparatus for supplying output power, it is oftentimes necessary to make an allocation between each apparatus in terms of how much power is to be supplied by each apparatus to obtain a desired total power output. The choice of power output from each apparatus can be a simple division of the total power output desired divided by the number of apparatus. However, such a simple and straight forward approach will oftentimes result in a high inefficiency, or put another way, the cost per unit of output power will most likely not be minimal. (The unit of output power can be pounds of steam, watts, BTUs, . . . .) For example, one of the major challenges in the pulp and paper industries is the optimization of steam production rates for plant boilers. Significant cost savings result when plants are switched from a manual allocation system to a computerized allocation system. In present systems, automated solutions have been implemented on mini-computers and have been expensive to implement and provided slow and incomplete service when implemented. The present invention provides a solution to the problems of these present day systems. Thus it is desired to make an allocation of power output to be supplied by each power output apparatus such that the overall cost of the power supplied is minimal, i.e., an economic load allocation of the power output apparatus, and on a real-time basis.
In the preferred embodiment of the present invention, a method for allocating an output load between a plurality of boilers to supply steam most economically will be described; however, the method will be equally applicable to cooling towers, chillers, air conditioners, turbines, . . . .
Some present systems can only perform an economic load allocation for systems which have efficiency curves characterized by linear equations. The method of the present invention can be utilized for any algebraic efficiency characterization equation and yield a complete solution in substantially fewer iterations than previous techniques.